Table 1 shows the measured reflection of a number of
materials which are important for the practical use of
sensors. The values of the collector current given are
relative and correspond to the reflection of the various
surfaces with regard to the sensor’s receiver. They
were measured at a transmitter current of IF = 20 mA
and at a distance of the maximum light coupling.
These values apply to all reflex sensors. The
‘black-on-white paper’ section stands out in table 1.
Although all surfaces appear black to the ‘naked eye’,
the black surfaces emit quite different reflections at a
wavelength of 950 nm. It is particularly important to
account for this fact when using reflex sensors. The
reflection of the various body surfaces in the infrared
range can deviate significantly from that in the visible
range.